1. Field of the Invention
This invention concerns a support cap of telescopic construction. More particularly, the support cap of telescopic construction, to which the invention relates, has been conceived especially for the exploitation of coal in steep seams by ascending cuts; the applications of the invention are not, however, limited to such use by this fact.
The exploitation of steep seams by ascending cuts or roads requires a support that can be advanced progressively as a cut or road is worked out, starting from the higher level of the packing of the preceding cut.
2. Description of the Prior Art
Some research has been done to adapt modern self-advancing hydraulic supporting means to steep seam working sites. This research has resulted in very heavy and very expensive apparatus the use of which has not spread and is not practical. One such apparatus is described in French Pat. Specification No. 2,087,724. It generally consists of frames formed of beams and a metallic cap. The frames are borne by penetrating into the packing and have to be lifted from one cut or road to the next. This manner of supporting presents many drawbacks as follows: the weight of the apparatus and its high cost, the difficulties in adapting it to irregularities in the surrounding rock and the fact that resistance to vertical forces, resulting from friction of the beams in the packing, is often insufficient or unreliable.